Deeply-etched 1 micron-thick silicon layers enabling 170-NM bandwidth highly-reflective Bragg mirrors

Deeply-etched distributed Bragg reflectors are demonstrated experimentally on silicon with mirror bandwidth that is larger than 170 nm. The reflector is realized by two layers of silicon 1-μm thick separated by a 1.95-μm air gap. Etching depth of 80 μm was obtained with side-wall angle better than 0.05 degree and scalloping peak-to-peak roughness of 15 nm. An optical filter was formed by two reflectors separated by a filter gap of 7 μm and the corresponding measured linewidth is 5 nm around 1550 nm wavelength. The estimated reflectivity of the mirror is larger than 96%. The reported micromirrors and filter enable the realization of on-chip wideband systems.